The need for radiation detecting materials has been at the forefront of materials research in recent years due to applications in national security, medical imaging, X-ray detection, oil well logging, and high-energy physics. There has been a growing interest in the development of scintillator materials with (1) good stopping power for gamma rays, (2) high light output, (3) proportional response, and (4) large, transparent, low cost crystals. For gamma-ray detection, several known inorganic scintillators, such as bismuth germanium oxide (BGO) and lutetium oxyorthosilicate (LSO), are currently being utilized in various radiation detection devices. Although these scintillators have good luminosity, their scintillation properties (decay times, linearity, etc.) are lacking in one or more areas. Other known scintillators, such as NaI:Ti, BaF2, and LaBr3:Ce, also fall short in one or more of these properties. Within the last decade, researchers have reported significant scintillation in the cerium-doped binary lanthanide halides. Additionally, Ce3+-doped ternary lanthanide halides, particularly those containing alkali metals, exhibit high luminosities (>20,000 ph/MeV) and fast decay times (<1 μs).